Quantification of Human Hair Moisturization with Cosmetic Products by Dynamic Vapor Sorption.

An attempt has been made to evaluate and quantify the moisturizing efficacy of cosmetic products by dynamic vapor sorption method. The possibility of quantifying this effect by the application of the second law of thermodynamics to sorption hysteresis has been demonstrated. The results show that the ordinary conditioner actives in rinse-off formulations show limited moisturizing capabilities. However, specially formulated products can show, quantifiably, both moisturizing and desiccating effects. From the Brunauer, Emmett and Teller (BET) theory, total pore volume obtained from the literature by nitrogen adsorption, and the sorption data from this work, it has been possible to show that the sorbed water in hair does not distribute uniformly in the hair. This is in agreement with the X-ray diffraction measurements and the more recent work on small angle neutron scattering on D₂O-saturated hair.